How to use First Aid in Disk Utility to check and repair APFS storage, whether it’s part of your boot disk, or general storage.
troubleshooting
Although your Mac may be unable to boot into macOS, it might be able to start up in Recovery, or offer its internal SSD in Target Disk Mode.
Multiple requests for a keychain password, login password mismatch, broken keychains, expired certificates, and using the Data Protection keychain.
Repairing permissions has a long history in Mac OS X. The permissions concerned have changed over the years, and it’s no longer what it once was.
Still very useful procedures for Intel Macs, resetting the SMC within a T2 chip is more complex. Used wisely they can resuscitate a failing Mac.
When should you turn iCloud off to try to solve syncing problems? What use is a Content Caching server? What tools can help diagnose and fix problems?
You point Safari at a website, maybe one you visit regularly, and it can’t connect. What do you do next to solve the problem quickly and efficiently?
How to plan and assemble faster backup systems for Time Machine, whether to change I/O policy, and how to minimise their size using exclusions.
As macOS doesn’t have a dashboard to warn you of dangerous security settings, it’s worth checking them. Here’s what to look for, and how to correct them.
What can you do when your Time Machine backups stop running regularly? Or another background activity has gone missing?
The Eclectic Light Company 